The present applicant possess a patent right for a wheel for sliding windows and doors patent-registered on Mar. 15, 2013 by applying a patent for “Wheel of Sliding Windows and Doors Having Preventing Eccentric Structure of Horizontal Rotation Wheel (Application No. 10-2011-0120393”) on Nov. 17, 2011.
The patent relates to a wheel for sliding windows and doors in which two or more inclined surface rolling wheels 10 having lateral contact surfaces are coupled to one transfer bracket 20 and contact a pair of diagonal surface guides 32 configured on a guide rail 30, respectively to support an upper load by respective generated reaction force and the respective inclined surface rolling wheels 10 move while rotate in opposite directions during moving and characteristic contents of the technology will be described below.
As illustrated in FIGS. 1A, 1B and 1C, provided is a structure in which a transfer bracket 20 is formed one or more coupling grooves 22 are formed in a vertical direction, an inclined surface rolling wheel 10 is molded while being integrated with a rotational shaft 12 in an orthogonal direction, a radial bearing 40 axially installed on the rotational shaft 12, and a thrust bearing 50 in which a lower race 54 is coupled to the top of the inclined surface rolling wheel 10 are constituted and coupled.
There is a technical characteristic that the top of the inclined surface rolling wheel 10 having an integrated structure with the rotational shaft 12 in the orthogonal direction maintains the orthogonal direction by the radial bearing 40 and the transfer bracket 20 to prevent the rotational shaft 12 from being tilted from a contact portion of the inclined surface rolling wheel 10 and the guide rail 30 in an opposite direction and an anteroposterior direction and prevent the lower race 54 in a thrust bearing 50 from drooping as the rotational shaft 12 is tilted, and as a result, upper and lower races 52 and 54 maintain a predetermined gap and drivability and rollability are secured by dispersing force to a ball or a roller.
However, the technology has a technical limit due to reasons described below.
First, there is a limit in durability depending on oxidation of an oil film and intrusion of foreign materials.
In general, the thrust bearing 50 supporting a vertical load is constituted by the upper race 52 and the lower race 54 and the ball or roller is installed therebetween and the oil film is formed on the surface to maintain a minute gap between the upper race 52 and the lower race 54 and as a result, the thrust bearing 50 is smoothly driven.
However, when the oil film is broken, the ball and the roller directly contact the upper race 52 and the lower race 54, and as a result, friction force cannot but increase and the friction force degrades the rollability and the durability of the bearing.
The oil film is broken due to reasons including oxidation of a lubricant depending on inflow of dust, foreign materials, and air, generation of rust depending on inflow of moisture, and the like because the ball or roller is not normally sealed.
However, in the case of a coupling structure of the thrust bearing 50 and the inclined surface rolling wheel 10 in the related art, as a structure in which the upper race 52 of the thrust bearing 50 is fixed to a lower part of the transfer bracket 20 and the lower race 54 is fixed to an upper part of the inclined surface rolling wheel 10 to rotate in opposite directions, since outer diameters of the upper race 52 and the lower race 54 are just exposed to the outside as illustrated in FIGS. 1A, 1B, and 1C, it is actually impossible that the thrust bearing 50 and the inclined surface rolling wheel 10 are completely sealed.
Accordingly, the foreign materials which repeatedly flows in need to be cleaned and the lubricant needs to be supplied in order to maintain an appropriate oil film since an action for the maintenance is not easy in terms of a general consumer or user, it is very difficult to overcome the limit in durability.
Second, there is a problem in that driving deteriorates due to generation of bearing eccentricity depending on a limit in load dispersion.
In the case of a load dispersion structure of the roller in the related art, the inclined surface rolling wheel 10 has a contact structure configured by an inclined surface on a line of the guide rail 30, and as a result, force to be tilted in an opposite direction to the contact is generated and the inclined surface rolling wheel 10 is thrust to a lateral surface while sliding on the inclined surface as illustrated in FIG. 1C.
In the tilting and the lateral thrusting, the rotational shaft 12 is erected while maintaining the orthogonal direction by the radial bearing 40 fixed to the transfer bracket 20.
According to the erection structure, the inclined surface rolling wheel 10 maintains a horizontal direction with the transfer bracket 20 and a predetermined gap is maintained between the lower race 54 of the thrusting bearing 50 fixed to the top of the inclined rolling wheel 10 and the upper race 52 of the thrusting bearing 50 fixed ton the bottom of the transfer bracket 20 to secure rotation smoothness of the thrust bearing 50.
However, in such a structure, when a predetermined load or more is applied, a concentration load generated at the contact of the guide rail 30 acts as force which concentrates on the radial bearing 40 and the thrust bearing 50, and as a result, the rotational shaft 12 is eccentric.
A bearing layout structure of the related art is a structure in which the lower race 54 of the thrust bearing 50 is fixed in a circumferential direction around the rotational shaft 12 at the upper part of the inclined surface rolling wheel 10 and multiple balls or rollers are uniformly distributed in the circumferential direction around the rotational shaft 12. Based on the contact of the inclined surface rolling wheel 10, provided is a structure (multiple balls or rollers are substantially distributed in the circumferential direction) in which the ball or roller is disposed at a left side and a right side around the rotational shaft 12 as illustrated in FIG. 1B.
Accordingly, a predetermined vertical load or more is applied, larger reaction force generated at the contact of the inclined surface rolling wheel 10 and the guide rail 30 is directly applied to the lower race 54 separated from the rotational shaft 12 or a lateral part of the ball to guide eccentricity of the inclined surface rolling wheel 10 or the rotational shaft 12. Such an eccentricity phenomenon is more significantly exhibited by the tilting phenomenon of the rotational shaft 12 and the lateral thrusting of the inclined surface rolling wheel 10.
The radial bearing 40 is completed by inserting the ball or roller between an inner ring and an outer ring and an assembly tolerance of a predetermined gap therebetween occurs during an assembly process.
Further, the radial bearing 40 is inserted and fixed into the coupling groove 22 of the transfer bracket 20 and in this case, a coupling tolerance also occurs. The coupling tolerance occurs even in the course in which the rotational shaft 12 is axially installed on the inner ring of the radial bearing 40. Occurrence of the coupling tolerance, that is, the assembly tolerance and the assembly tolerance of the rotational shaft 12, and a clearance of the radial bearing 40 causes a minute tilting phenomenon of the rotational shaft 12 and the lateral thrusting of the inclined surface rolling wheel 10.
Further, in the related art, a layout position of the radial bearing 40 preventing horizontal tilting is also separated from the contact of the inclined surface rolling wheel 10 which is a tilting occurrence point due to the layout position of the thrust bearing 50, the radial bearing 40 is installed at a position not to relatively effectively prevent the tilting.
The minute tilting of the rotational shaft 12 consequently damages a uniform gap between the upper race 52 and the lower race 54 required for normal rotation of the thrust bearing 50 to concentratively apply the load on the ball or roller at a specific position, thereby significantly deteriorating the drivability or rollability of the inclined surface rolling wheel 10.
In addition, in the structure of the roller in the related art, there is a problem related with a limit in maintaining the durability of the bearing depending on sealing vulnerability and there is a problem in that the load is usable only within a limited range so as to prevent a driving trouble from being occurred due to eccentricity by biasing.